Thermoplastic polyolefin (TPO) based roofing membranes are one of many types of roofing membranes available on the market today. TPO may be a melt blend or reactor blend of a polyolefin plastic, such as a polypropylene polymer, with an olefin copolymer elastomer (OCE), such as an ethylene-3Q propylene rubber (EPR) or an ethylene-propylene-diene rubber (EPDR). Examples of commercially available TPO membranes include SURE WELD™ (Carlisle Inc.), GENFLEX™ (Omnova Solutions, Inc), ULTRAPLY™ (Firestone Building Products) and EVERGUARD TPO™ (OAF). Novel stretchable TPO membranes are disclosed in U.S. Pat. No. 7,666,491, which is incorporated by reference herein.
TPO based membranes may also be used as geomembranes to cover landfills, storage ponds of water, and the like. Such TPO membranes may have a higher polypropylene content than a similar TPO roofing membrane and sometimes they are referred to as fPP (flexible polypropylene) membranes or sheets.
TPO-based roofing membranes may comprise one or more layers. A TPO membrane may comprise base-(bottom) and cap-(top) layers with a fiber reinforcement scrim (middle) sandwiched between the other two layers. The scrim may be a woven, nonwoven, or knitted fabric composed of continuous strands of material used for reinforcing or strengthening membranes. The scrim is generally the strongest layer in the composite. The fabric can contribute significantly to the tensile strength of the roofing membrane and provide for dimensional stability. In an example, the fabric reinforcement comprises a polyester yarn based scrim. Glass fiber based scrims may also be used for situations where additional weight and/or improved dimensional stability are desired.